Optoelectronic sensors are relatively well known in the art and have been utilized in the prior art as shaft encoders and other movement detectors. In at least one prior art optoelectronic movement sensor, a single light detector is utilized in conjunction with a light source opposite a patterned reticle. The major problem with this structure is that the amplitude of the output signals is dependent upon the brightness of the light source.
In another prior art structure, two light detectors are utilized but they are incorporated into a single semiconductor chip and, thus, the light detectors have a fixed relative position. This is a serious problem since in many instances the reticle must be constructed in a certain form or size. By fixedly positioning the light detectors in a single semiconductor chip, the size and spacing of the light detectors is severely limited, which severely limits the size and shape of the reticle and interupter.
In another prior art structure, two light detectors are utilized separately with one or two light sources. The outputs of the two light detectors are applied to operational amplifiers to obtain a linear output signal. This linear signal is utilized in the micrometer and submicrometer range for the adjustment of optical waveguides. While this device is useful for accurately positioning relatively small or precision items, it is not convenient for use in sensing relatively large movements or direction of the movement. This is especially true if the signals are being applied to digital circuitry, such as a microprocessor, since A/D converters or the like must be used and the cost and size becomes prohibitive.